Booeymonger supplies Vital Vittles with pre$-$made sandwiches that are then retailed to the Georgetown campus community. These sandwiches retail, on average, for $$6\mathrm{.}75$ and Vital Vittles takes a margin of $25\%$ of the retail price. Booeymonger's variable costs to make and deliver the sandwiches are, on average, $$2\mathrm{.}15.$ Like many other retailers, Vital Vittles charges Booeymonger a shelving fee and a licensing agreement that together amount to $$15,000$ per year.

$2$a$.$ What is Booeymonger's unit margin?

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